WO2002013596A1

WO2002013596A1 - Modular grass stadium surface using grass units and forced air

Info

Publication number: WO2002013596A1
Application number: PCT/US2001/024579
Authority: WO
Inventors: B. Scott Clark; John H. Hilson, Iii; Walter Bray
Original assignee: BURTON F CLARK Inc
Current assignee: BURTON F CLARK Inc
Priority date: 2000-08-10
Filing date: 2001-08-06
Publication date: 2002-02-21
Anticipated expiration: 2003-02-10
Also published as: AU2001278168A1; WO2002013596A8

Abstract

A turf system comprising a plurality of turfgrass units (4) having sidewalls for containing plant growing medium (6), in combination with means for providing forced air under and around the units. The growing medium comprises a turfgrass layer, an irrigation layer, and a rootzone layer between the turfgrass layer and the irrigation layer. The turfgrass units have fastening members that interconnect for releasably attaching each unit to at least one other unit. When assembled into a turf array, the system provides air duct channels forming a channel system (10). A pump is used to force air through the channel system and a heater may optionally be used to heat the air. The pump forces the heated air through the channel system and through the irrigation layer to the rootzone layer. Atomizing nozzles are used to inject water into the air provided to the channel system, in order to modify the humidity of that air. This provides necessary water to the rootzone layer of the turf units, and also results in evaporation cooling of the growing medium.

Description

MODULAR GRASS STADIUM SURFACE USING GRASS UNITS AND FORCED AIR

FIELD OF THE INVENTION This invention relates generally to an apparatus for providing turf for a sports field, in a modular form, that includes a way to treat and maintain the turf and the subsoil rootzone.

BACKGROUND OF THE INVENTION This invention is directed to an improved modular turfgrass unit for natural turf surfaces, such as those in stadiums, playing fields, and parks. Stadiums host numerous events, such as sporting events, associated practice sessions, and concerts. Playing fields, such as those at schools and recreational parks, receive heavy daily use for a multitude of events. During events, such as a football or soccer game, the grass surface receives an incredible pounding that causes substantial damage to both the turfgrass and the underlying soil layer, including the rootzone. Many times the damage is so severe that the playing field cannot be used for a number of days following the event. The time period which it takes the turfgrass to recover is extended if the weather is poor during the event causing the damage. Rain, during even a portion of a sporting event, can cause the grass surface to become very soft, such that the damage caused by people treading on it is more severe, rendering a playing field useless for up to a week or even longer.

Occasionally, the damage is so bad, that some or all of the turfgrass is unsalvageable and a new field must be constructed by removing the damaged turfgrass and laying down fresh sod. The removal of the damaged turfgrass and its associated rootzone involves the use of manual or powered cutting tools, and fresh sod must be brought in and cut to fit the required areas. The fresh sod must then be allowed to become fully integrated with the field. This process is time-consuming and costly. One solution to the problem of damage to grass surface is the use of synthetic turf, such as Astroturf®. Because Astroturf® is a strong synthetic material, it solves the problem of turf destruction, allows multiple and repeated use of a playing field, and is relatively maintenance free. Accordingly, it is widely selected by those constructing, owning, or caring for fields. Synthetic turf, however, is not without its detractors, in particular, the athletes who play on the surface. In addition to looking and feeling nothing like natural grass, Astroturf® is generally laid down over a layer of concrete or other hard material and, therefore, provides an extremely hard. Artificial grass also has very different frictional characteristics from real turfgrass and as such, many athletes prefer real turfgrass to artificial grass. Natural grass fields are, therefore, often the preferred type of playing field to those using the field. Manufacturers have developed alternative turfing systems for playing fields in which grass is grown and maintained in a plurality of turf units, is transported to the desired location, and is configured, in a puzzle-like manner, into a playing field. This construction can be accomplished within a short time period and, after use, the field may be disassembled and transported to another location. Any damaged turf units can be replaced as desired or necessary.

For example, U.S. Patent No. 5,187,894 ("the '894 patent") discloses natural turf units that are transportable and comprise sand fractions and pieces of expandable polymer that is inert to plant growth chemistry. U.S. Patent Nos. 5,467,555 ("the '555 patent") and 5,595,021 ("the '021 patent") disclose natural turf units that are transportable and comprise a fence section hingeably connected to the growing pan of the turf unit that maintains the grass at a proper height above the side walls of the growing pan. The '894, '555, and '021 patents are incorporated herein by reference.

In many soil related environments, it is important to maintain the soil and turf temperature at a desired level. Examples include greens found on golf courses and sports stadium playing fields. The grasses used in their construction can be temperature sensitive and in some cases, cannot tolerate even relatively small changes in temperatures beyond their adaptation range (i.e., bent grasses used on some golf courses). The grass can be quickly damaged if special precautions are not taken to protect it from such temperature excursions.

To date, field heating systems developed and used to control the temperature of turf systems fall into two primary types. The first type is hydronic systems, in which a water and/or glycol solution, heated with boilers, is transfeπed through a series of subsurface pipes. These pipes are typically buried 8 to 12 inches deep in the soil. The presence of these pipes makes field repairs and maintenance difficult. These hydronic systems heat conductively and are, therefore, significantly warmer near the conduit than near the surface of the field. This heat gradient results in soil temperatures near the conduit that are too warm and soil temperatures near the grass surface that are too cool. The second type of field heating system consists of air systems in which indirectly heated air is transfeπed through a series of perforated subsurface pipes. A hot air furnace is used to directly heat a first mass of air - this air, through a heat exchanger, is used to indirectly heat another mass of air. A blower forces this indirectly warmed air through the subsurface perforated pipe network, such that the system operates convectively, forcing the warmed air directly through the root zone of the grass.

Due to this convective process, the temperature gradient between the duct system and the surface is reduced as compared to hydronic systems. However, a temperature gradient does develop with distance from the injection point. The gradient issue has typically been addressed by constructing the perforated distribution pipes on relatively close spacing ranging from five to twenty feet. Another problem that occurs with these indirect, fired systems is depletion of the soil moisture as the hot dry air is directed through it. This type of heating system is also very inefficient due to losses occurring in the heat exchanger. However, it is widely accepted in the art that the directly heated furnace air should not be used to heat the grass, based on the belief that combustion products in the direct-fired air would adversely affect the health of the grass. The heated air has also been prone to leaking out through undesirable pathways.

For example, U.S. Patent Nos. 5,433,759 ("the '759 patent"), 5,596,836 ("the '836 patent"), and 5,636,473 ("the '473 patent") disclose systems of treating soil and turf by pumping or drawing forced air through the soil profile of the turf via an underground network of ducts. The air is supplied by a blower that can be connected to the underground duct network in selective manner (by a 4-way valve or other means of connecting the blower) so the air flow can be reversed for drawing air through the soil profile. A supply tank is connected to the piping between the blower and the underground network so that soil treatment materials (e.g., fertilizers, insecticide, fungicide, etc.) can be introduced to the forced air to aid in the treatment of the soil. Soil temperature may also be controlled with heat exchangers located between the blower and the underground duct network so that the soil temperature can be controlled. U.S. Patent No. 5,507,595 ("the '595 patent") discloses a system of treating soil and turf by pumping or drawing forced air through the soil profile of the turf via an underground network of ducts, in which a moisture separator unit is located between the air blower unit and the underground duct network, such that the moisture level of the air being communicated between the blower and the soil can be controlled and any coπosive chemicals, that can be harmful to the blower mechanism, can be removed. U.S. Patent Nos. 5,542,208 ("the '208 patent") and 5,617,670 ("the '670 patent") disclose a mobile air blower unit to be used in conjunction with the soil and turf treatment system/method disclosed in the '759, '836, '473, and '595 patents. The mobile unit can be self propelled for ease of moving from one turf field to another. U.S. Patent No. 5,120,158 ('"the '158 patent") discloses a pipe arrangement for a playing field which includes a surface layer and a filter layer beneath the surface layer. The filter layer contains an arrangement of pipes to dry the field and to circulate warm air into it. The '759, '836, '473, '595, '208, '670, and '158 patents are incorporated herein by reference. There is a need, therefore, for a modular unit of natural turf grass that is both transportable and that can be connected in a manner as to further allow temperature and/or humidity control, and measuring thereof, of the grass surface and rootzone layer in the modular unit. The present invention is directed to such a unit.

SUMMARY OF THE INVENTION The present invention is directed towards an improved modular turf system. The system may comprise a plurality of turf units, and an air pump. The turf units may be disposed on an underlying surface in proximity to each other to form a turf unit array having a turf surface. The turf units, which may have a rectangular shape as viewed from above, may contain a plant growing medium in which a plurality of turf plants, such as turfgrass, is growing, the growing medium comprising a rootzone layer and a drainage layer. The turf system may optionally contain a heating system for heating the airstream. The rootzone layer may comprise a mixture of processed sand and peat, and may have a depth of about 5 to 7 in. The drainage layer may comprise gravel , and may have a depth of between about 3 to 5 in. . In one embodiment, the growing medium has a first temperature and the air has a second temperature. Preferably, the second temperature is less than about 70% greater than the first temperature and more preferably, the second temperature is less than about 50% greater than the first temperature. In another embodiment, the first and second temperatures have a difference of less than about 40 °F. In a prefeπed embodiment, the difference is less than about 10°F. In an alternative embodiment, the second temperature is between about 70°F and about 120°F. Preferably, the second temperature is between about 70 °F and about 80 °F. In yet another embodiment, further comprising a system for introducing a liquid into the airstream.

The turf unit array has an outer surface which faces the underlying surface; together, these surfaces form a channel system through which air can flow. The pump operates to force the air through the channel system and into the rootzone layer of at least one of the turf units.

Optionally, the heating system may be used to heat the air. The heating system comprises a direct-fired furnace which directly heats the air which is forced through the channel system. Alternatively, the heating system may comprise a direct- fired furnace and a heat exchanger, the furnace heating a first body of air and the heat exchanger transferring some of the heat energy from the first body of air to a second body of air without mixing of the first and second bodies of air, the second body of air being forced through the channel system. The system may include a plurality of locator pads interacting with the turf units, these locator pads providing repeatable alignment of the turf units with substantially no gaps in the turf surface. The turf system may further include one or more warning track units used alone or in conjunction with the turf units.

The turf system may further comprise atomizing nozzles disposed in the channel system. Such atomizing nozzles can be used for injection of atomized fluid (such as pure water or water with other components mixed in) into the airstream in the channel system. The injection of water through the atomizing nozzles can effect cooling of the turfgrass rootzone layer relative to the temperature of the rootzone layer prior to injection of the water. In alternative embodiments, a liquid or a particulate matter may be introduced into the airstream. The turf system may further comprise one or more sensors sensing one or more system physical parameters, the parameters being selected from the group of rootzone temperature, channel system air temperature, rootzone moisture content, channel system air humidity, rootzone gas concentrations, and channel system air pressure. If the system includes such sensor(s), it may further comprise a closed-loop control system for control of the relevant system physical parameter(s).

For example, the turf system may include a sensor sensing the rootzone moisture content and generating a signal based thereon. This turf system could then further include a closed-loop control system, responsive to the signal, provided with a predetermined setpoint value for the rootzone moisture content, the closed loop control system controlling one or more of the heating system, pump, and atomizing nozzles, so as to bring the sensed rootzone moisture content closer to the setpoint value. Alternatively, the turf system could include a sensor sensing the rootzone temperature and generating a signal based thereon. This embodiment could then further include a closed-loop control system, responsive to the signal, provided with a predetermined setpoint value for the rootzone temperature, the closed loop control system controlling one or both of the heating system and the pump so as to bring the sensed rootzone temperature closer to the setpoint value.

In another embodiment, the turf system of the present invention may comprise a plurality of turf units, a heating system, a pump, one or more sensors, and a closed-loop control system. Each turf unit contains a plant growing medium in which a plurality of turf plants is growing. The turf units are disposed on an underlying surface in proximity to each other to form a turf unit array. The turf plants of the turf unit array form a grass surface. Each turf unit has a lower surface; the lower surfaces of the turf units in the turf unit array, with the underlying surface, form a channel system through which air can flow. The system further includes a heating system for optionally heating the air and a pump for forcing the air through the channel system and into the rootzone layer of at least one of the turf units. The system further includes one or more sensors for sensing a system temperature and generating a signal indicative thereof, the system temperature being selected from the group of: (i) temperature of the air in the channel system or (ii) temperature of the rootzone layer. Finally, the system includes a closed- loop control system, responsive to the signal from the sensor(s) and a predetermined system temperature setpoint value, controlling at least one of the pump and the heating system, such that heated air is supplied to the rootzone layer of at least one of the turf units when the signal from the sensors indicates a system temperature below the setpoint value.

DEFINITIONS

As used herein, the term "turf refers to the upper layer of earth that is exposed to ambient air.

As used herein, the term "subsoil" refers to one or more soil layers that are situated immediately below the turf and may be made up of natural or prepared layers of various constituents such as sand, gravel, and mixes containing organic and other substances that might promote the growth and well-being of plant life.

As used herein, the term "about," as used with a range of numbers, refers to both the upper and lower numbers in that range.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of one embodiment of the turf unit, turfgrass, and rootzone layer of the turf system of the present invention.

FIG. 2 is a cross-section view of the turf units, turfgrass, and rootzone layer of the turf system of the present invention.

FIG. 3 is a plan view of a plurality of turf units of the present invention connected by foot locator pads.

FIG. 4 A is a plan view of a plurality of turf units of the present invention connected in a large array to form a playing field turf array. FIG. 4B is a close-up plan view of a portion of FIG. 4 A.

FIG. 5 is a perspective view, partially cut-away, of a warning track unit of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Turf Units With reference to FIG. 1, the turf system 2 of the present invention generally comprises modular turf units 4 that are constructed to contain growing medium 6 (also refeπed to as the rootzone layer) or soil for receiving turf plants 8, such as grass. A plurality of turf plants 8 are provided to the growing medium 6 of the turf unit. The root system of the turf plants 8 penetrates into the growing medium 6, forming the rootzone, an integrated mass of growing medium 6 and root structure. A plurality of the turf units 4, containing the turf plants 8 and root structure, may be placed side-by-side, to form a grass surface of any desired shape or geometry. For example, FIG. 4A shows a plurality of rectangular turf units installed for a soccer playing field. The turf unit 4 typically includes a growing pan 5 or turfgrass unit having side walls 12. The turf unit may be constructed of any material sufficiently strong and light enough to structurally support the turfgrass and growing medium 6. Preferably, the growing pan is molded from a durable plastic material. More preferably, the growing pan is molded of high density polyethylene. Whatever material is selected, preferably it has a high strength-to-weight ratio, such that it is both physically durable and also light in weight so as to facilitate transportation. Other forms of a growing pan may be employed, such as those having different geometries. A baffling aπangement comprising baffles are preferably provided within the interior of the growing pan. Baffles facilitate settling of the growing medium 6 within the growing pan. Units as described above are commercially available from GreenTech of Richmond, VA under the trade name Integrated Turf Management ("ITM®") System.

The growing pans may be provided with an undersurface shaped such that assembly of a plurality of the turf units 4 creates an integrated air duct channel system 10 within the network of turf units 4. As discussed in more detail below, this air duct channel system 10 allows access to the root system by forced air, such that the temperature and general growing environment may be controlled and optimized.

A wide variety of geometries may be employed in the utilization of turf units 4 of the present invention. While rectangular turf units 4 are preferred, other geometries, such as triangles, hexagons, or trapezoids, may be used to obtain similar results. The geometry is not critical, however it is preferable that the selected geometry is one which will cover an area with no gaps between the turf units. It may in fact be prefeπed to employ non-rectangular geometries for activities having sidelines that are not rectangular in shape (cricket, for example), such that the field borders coincide with the seams in the pattern of turf units 4. The rootzone mix layer is preferably maintained at a significant height above the top of the side walls 12 of the growing pan while the turf unit is at a remote storing location, as well as during transport of the turf units 4 to the field. A removable or articulating retaining barrier 19 may optionally be used in conjunction with the growing pan 5 to provide an initial barrier for maintaining the growing medium 6, as well as the turf plants 8, at the desired height above the side walls 12. As seen in FIG. 2, removal or articulation of the barrier out of its retaining position when the turf units are combined in the final assembled system allows the rootzones 6a and 6b of adjacent turf units 4a and 4b to come into direct intimate contact with each other, thus presenting a seamless grass surface with no "gaps" at the boundaries between adjacent turf units.

In the embodiment of the system shown in FIG. 1, the barrier comprises a hinged fence. With the fence in the "closed" (up) position 19a, the growing medium 6 and the turf plants 8 can be filled into the growing pan up to a level near the top of the fence. When it is time to assemble a continuous natural grass playing surface, a plurality of turf units 4 are transported to the desired field location with the fence in the closed (up) position. Just prior to assembly of the field, the fence is folded into the "open" (down) position 19b such that a substantial portion of the growing medium 6 and turf plants 8 are at a significant height above the level of the top of the growing pan side walls 12. Referring to FIGS. 3 and 4, a plurality of turf units 4 are preferably arranged in the desired geometric configuration of the playing field 14, for example. The turf units may simply be placed in their desired positions, such that friction with the underlying surface will hold the units in place. Preferably, however, the position of the turf units is maintained, either by fastening means or locating means. Fastening means may be used to fasten together adjacent turf units, so as to maintain the contact between (i.e., intimate relative position of) adjacent units, thus forming an integrated turf field 14. Locating means may be used to maintain the location of turf units in an absolute sense in the reference frame of the underlying surface.

The fastening means may include physical interlocking of the side walls of adjacent turf units, in the manner in which jigsaw puzzle pieces interlock, or may comprise clips which hold together the edges of the side walls of adjacent units.

In a prefeπed embodiment of the present invention, the locating means can comprise locator pads 16 having a plurality of cone locators 18 extending up from the locator pads 16. When the turf units 4 are placed into position to construct the playing field 14, the turf units 4 are disposed onto the locator pads 16 such that the cone locators 18 are received by coπesponding wells in the bottom surface of the growing units. When the turf units 4 are in the prefeπed square shape, the four cone locators 18 at the corners of locator pads 16 conveniently locate the growing units into position and hold the growing units in place adjacent each other. The combination of the locator pads 16 and the cone locators 18 cause the turf units 4 to be pressed together, causing a compressive force at any gaps and/or seams in the system, allowing the air to flow preferentially away from the seams/gaps and into the more permeable growing medium. Thus, the location of adjacent growing units is positively maintained, such that adjacent turf units 4 do not separate under the influence of the stresses exerted on the playing surface by the athletes using the turf.

Following installation of the turf units 4 into an operational field, the turf itself is then prepared for activities such as mowing, the application of field lines and markings, and the like. Following a particular activity, such as a football game, any or all the turf units 4 may be removed and transported to another location for treatment of damaged turfgrass, continued maintenance and growth. To achieve this, the turf units 4 are separated from each other, and the barriers are put back into place. If desired, the playing field 14 may be kept in the same location and worn areas may be replaced with healthy turf units 4 and/or the field dimensions or geometry may be altered for another sport (i.e., switching from a football game to a soccer game, each of which requires a field of different dimensions).

Turfgrass and Growing Medium

A wide variety of turf plants 8 may be used with the present invention. Preferably, the turf plant is a grass. Any one of a number of turfgrass species may be employed. The turfgrass species may be selected for the particular growing conditions extant in the areas where the turf is to be grown and maintained. A plurality of turfgrass species may be used, such as bentgrass, rye, bluegrass, and zoija, and, additionally, blends of grasses, such as Kentucky-blue grass, perennial ryegrass, fescues, Bermuda grasses, and bentgrasses may be also employed depending upon the particular circumstances of each installation. The most prefeπed turfgrass in accordance with the present invention is bluegrass sod. One of ordinary skill in the art would be able to properly make the selection, seeding, nurturing, and maintenance of these turfgrasses. The above-mentioned turfgrasses may be obtained from a number of manufacturers, such as Tuckahoe Turf Farms, Inc. of Hammonton, NJ, Jade Run Turf & Sod Farm of Bethel, DE, or Saratoga Sod Farm of Stillwater, NY.

The turfgrass is placed on top of a rootzone layer 6, where it is allowed to grow into a healthy grass surface. The rootzone layer 6 may comprise any material sufficient to nurture the desired type of turfgrass. Preferably, the rootzone layer 6 comprises a mixture of processed sand and peat. The rootzone layer 6 preferably has a depth of about 5 to 10 in and more preferably, a depth of about 5 to 7 in. The rootzone layer 6 may be of homogeneous thickness or have varying thickness across the cross- section of the turf unit. The rootzone layer 6 composition may be varied to provide optimum growing medium 6 for prefeπed grass and/or location of field.

The sand for the rootzone mix may be of any type and particle size. Preferably, the sand is processed sand (washed) and has particles of uniform size, typically accomplished by screening. In a prefeπed embodiment, the processed sand of the rootzone mix comprises various fractions having the following sizes: gravel, very coarse, coarse, medium, fine, very fine, silt, and clay. The gravel (10 U.S. Standard Sieve) preferably has a diameter of up to about 2 mm and is present in an amount of no greater than 3% of the total sand. The very coarse (18 U.S. Standard Sieve) sand preferably has a diameter of up to about 1 mm and is present in an amount of no greater than about 10% of the total sand. More preferably, the combination of gravel and very coarse sand should not exceed 10% of the total sand. The coarse (35 U.S. Standard Sieve) sand preferably has a diameter of up to about 0.5 mm and is present in an amount of at least about 60% of the total sand. The medium (60 U.S. Standard Sieve) sand preferably has a diameter of up to about 0.25 mm. The fine (100 U.S. Standard Sieve) sand preferably has a diameter of up to about 0.15 mm and is present in an amount of not more that about 20% of the total sand. The very fine (270 U.S. Standard Sieve) sand preferably has a diameter of up to about 0.05 mm and is present in an amount of no more than about 5%. The silt fraction preferably has a diameter of up to about 0.002 mm and is present in an amount of no more than about 5% of the total sand. The clay fraction preferably has a diameter of up to about 0.002 mm and is present in an amount of no more than about 3% of the total sand. In a prefeπed embodiment, the coarse, medium, and fine sand components should not exceed 80% of the total sand. In another prefeπed embodiment, the very fine, silt, and clay components should not exceed 10% of the total sand.

The peat used in the rootzone mix may be of any type known to one of ordinary skill in the art. Preferably, the peat is standard peat and is free of deleterious matter, such as sticks, stones, and hay. In a prefeπed embodiment, the peat has a total ash content of no more than about 15%. Preferably, the peat has a pH of about 6.5 to 7.5 and a moisture content of between about 30 to 50%. The peat particles may be of any size. Preferably, at least about 95% of the peat particles have a diameter of no more than about 2 mm and more preferably, about 100% of the peat particles have a diameter of no more than about 2 mm. Most preferably, at least about 80% of the peat particles have a diameter of no more than about 1 mm. The mixing of materials can be done by a number of methods known to one of ordinary skill in the art. The sand is typically present in an amount of between about 10 and 90 weight percent of the total mix and the peat is typically present in an amount of between about 90 and 10 weight percent of the mix. Preferably, the sand is typically present in an amount of between about 85 and about 95 weight percent of the total mix and the peat is typically present in an amount of between about 15 and about 2 weight percent of the mix. It is preferred that the mix meets criteria set forth in the 1993 USGA physical testing protocol (25 cm evaluation).

The resulting rootzone mix should have an infiltration rate of no less than 5 in/hr, preferably an infiltration rate of between about 2 and about 30 in/hr, and most preferably an infiltration rate of between about 10 to 18 in/hr. The rootzone mix bulk density should be no greater than about 5 g/cm3, preferably between about 1 and 3 g/cm³, and most preferably between about 1.2 and 1.6 g/cm³. The resulting rootzone mix should have a total porosity between about 30 to 70%, preferably between about 35 to 60%, and more preferably, between about 40 to 55%. The rootzone mix should have a saturation percentage between about 10 and 80%, preferably between about 20 and 70%, and more preferably, between about 30 and 60%. The organic matter (dry weight) of the rootzone mix should be greater than about 0.1%, preferably between about 0.1 and 5%, and more preferably between about 0.7 and 3%. Beneath the turfgrass layer and the rootzone mix is located a drainage layer, preferably of a gravel type. It will be understood that the growing pan 5 is provided with several openings in its surface which allow drainage out of the growing medium. The drainage layer preferably has a depth of about 1 to 8 in, and more preferably between about 3 to 5 in. The drainage layer of the present invention comprises washed and graded pea gravel (pea stone). The pea gravel stone size should be less than about 12.5 mm. It is prefeπed that no more than 10% of the pea gravel have a diameter of less than about 2 mm. In a most preferred embodiment, no more than 5% of the pea gravel has a diameter of less than about 1 mm. The pea gravel should have a uniformity coefficient of less than about 2.5 and meet at least one of the following criteria: have a sulfate soundness (C-88) of less than about 12% loss or have an LA Abrasion (ASTM C131) of less than about 40.

Forced Air

As seen in FIGS. 2 and 4 A, once the turf units 4 are connected, an integrated air duct channel system 10 is formed. The channels result from the combination of the outer surface of the growing pans and the underlying surface upon which the turf units are placed. It will be appreciated that the shaping of the undersurface of the growing pan embodiment seen in side view in FIG. 2, results in an interconnected rectilinear network of channels when a plurality of turf units are installed in a turf assembly, thus forming the channel system. The channel system 10 may be connected to a forced air system such that air, maintained at a desired temperature, may be forced through the system, to maintain the turfgrass at or near its prefeπed adaptation range. In another embodiment, the channel system 10 may be placed under a vacuum such that the rootzone layer 6 is concurrently under a vacuum to remove, for example, unwanted water from a heavy rain.

It will be understood that due to the openings in the growing pan, there is an air flow path which includes the region above the turf surface, the growing medium itself, and the channel system. For example, when the system is operated under pressure, air will be forced through the channel system, the openings in the growing pans, and up through the growing medium, to the outside atmosphere above the turf surface. Conversely, when the system is operated under vacuum, air will be drawn from the atmosphere above the turf surface, down through the growing medium, the openings in the growing pans, and into the channel system. It is this airflow mechanism that allows the temperature and humidity control which is discussed in detail below.

Typically, it is required to heat the air to above its ambient temperature, in order to warm the turfgrass, to above the ambient temperature, for example to prevent freezing of the turf plants. Systems for closed-loop control of air temperature and injection of the suitably heated air is well-known in the field of heating, ventilation, and air conditioning ("HNAC"). Such systems include a heating system 30 to heat the air, a pump or blower system 40 (with associated damper 42) to force the air through the system, and one or more air temperature sensors 50 to sense temperatures within the system. The signals from sensors 50, in conjunction with a predetermined setpoint specifying the desired temperature, provide the appropriate signals to command or control components of the system, so as to bring the sensed temperature closer to the setpoint. For example, the sensed temperature and the temperature setpoint may relate to the air temperature within the channel system or the temperature within the turf unit, such as the temperature within the rootzone.

The components of the system which are controlled to bring the sensed temperature closer to the setpoint include the heater (which may be turned on or off, or which may be proportionally controlled) the blower (which may similarly be controlled), the damper (which may be proportionally adjusted, or which may be switched to manifold the channel system to either the intake or the exhaust of the blower), or humidity control devices (which can indirectly affect system temperatures, and which are discussed in further detail below).

In one embodiment of the present invention, the heating system comprises a high efficiency, direct-fired natural gas or propane furnace 32 in combination with a heat exchanger 34. The furnace directly heats a first body of air, and via the heat exchanger, this first body of air provides heat to a second body of air. The blower 40 then forces the heated second body of air through the channel system 10. In this embodiment, the air that is being forced through the turf system does not contain any appreciable amounts of the combustion by-products generated by the heater furnace 32. Because the blower pressurizes the warm air in the channel system, it tends to migrate, through the openings in the bottoms and sides of the turf units, into the rootzone, thus heating the soil in the rootzone to the desired temperature.

The temperature of the forced air may be adjusted as necessary to provide optimal soil temperature of about 50 °F to 80 °F. Preferably, the air injection temperature is between about 60 °F and about 120°F and more preferably between about 60 °F to about 80 °F. The air injection temperature is preferably less than about 70% greater than the target soil temperature and more preferably less than 50% greater than the target soil temperature. In a most prefeπed embodiment, the air injection temperature is less than about 20% greater than the target soil temperature. In a preferred embodiment, the gradient in temperature between the injection points and the soil is less than about 70°F. The temperature feedback signal for the control system may be generated by one or more sensors placed in the soil within the turf units, or by sensors within the channel system.

In one embodiment of the present invention, a high efficiency, direct-fired natural gas or propane furnace is used to directly heat the air which is then forced into the channel system and thus through the rootzone and turfgrass. Experiments of this embodiment of the invention show that notwithstanding the general belief in the art that direct-fired air should not be provided directly to the grass, such direct-fired air can in fact be used to good effect, completely obviating the need for any heat exchange system. In this embodiment, the hot air "exhaust" of the furnace 32 is provided directly as the input flow for the channel system 10. Not wishing to be bound by any particular underlying scientific theory, it is believed that the combustion byproducts, water vapor and carbon dioxide, when injected into the turf, serve to increase grass growth potential by delivering beneficial nutrients to the system. The humidity byproducts aid in maintaining adequate soil moisture content and the carbon dioxide by product provides enriched carbon dioxide levels to the grass for photosynthesis during reduced light conditions. It is believed that the carbon monoxide produced as a combustion by product is not at levels toxic enough to affect the turfgrass system.

The embodiment of the turf system shown in FIG. 4A has a plurality of heating units 30 and blower units 40 which are manifolded, through a damper 42, to a large-capacity air discharge duct 44. The discharge duct communicates with the channel system 10 underlying the turf array 14 of the playing field. In the illustrated embodiment, there are six heating units and two blower units; however one of ordinary skill in the art will readily understand that the number and distribution of heaters and units in each particular installation is a matter of routine design choice based on numerous system characteristics.

Although the need in the art is primarily for a system to heat the turf when ambient temperatures are low, it is also possible to cool the turf system during more stressful summer temperature extremes. This may be accomplished in the embodiment of the system of the present invention (discussed in further detail below) which uses atomizing nozzles to inject fluid, such as water or nutrient-enriched water, into the air supplied to the channel system 10. By injecting cool atomized water into the air, the injection air stream is cooled significantly, ultimately resulting in a cooling of the turf system through conduction of heat from the turf to the water, and through subsequent evaporative cooling as that water evaporates. Alternatively, if the soil is sufficiently moist, the cooling can be achieved without the addition of water, but merely by blowing air not having added water, into the channel system. In yet another embodiment, the moisture content of the rootzone can be increased by irrigation (surface water application), followed by blowing air not having added water into the channel system.

In an alternative embodiment of the present invention, a heater may not be required, such in areas having a moderate climate. In this embodiment, the operation of the pump and/or blower puts energy into the airstream being acted upon, thereby inherently warming the injection air as it is compressed for entry into the system. Additionally, without being bound by any particular theory, it is believed that friction in the ducting system further contributes to warming the injected air; the combination of the above-mentioned effects may provide sufficient heating in moderate climates.

In another embodiment of the present invention, liquid, such as water or water containing additives, may be optionally added to the airstream by any system for introducing liquid into an airstream known by one of ordinary skill in the art. For example, a predetermined volume of liquid may be added into the airstream, such as an open pool or steady stream, which can evaporate and become entrained in the airflow. Additionally, a capillary system, such as a liquid-filled wicking medium, may be placed in the airstream or a simple nozzle having sufficient liquid velocity that the liquid is entrained in the airstream. Preferably, a liquid is optionally added to the airflow with an atomizing nozzle.

Alternatively, fine particulates, such as fertilizer, micro-organisms, pesticides, herbicides, or mixtures thereof, may be optionally introduced into the airstream. The particulates may be added be any method known to one of ordinary skill in the art, such as by the combination of a hopper or grinder situated to drop the particulate into the airstream.

Pressure Control

The pressure of the forced air that can be introduced to the channel system 10 may be varied. Preferably, the pressure ranges from about 4 to about 6 in of water column. Preferably, the injection pressure is less than about 10 in of water column. Without being bound by any particular theory, it is believed that lower injection pressure significantly decreases air leakage from the channel system 10. Measuring the pressure or moisture within the channel system 10 is accomplished by various known means. For example, automatic pressure sensors and/or moisture meters may be operated in conjunction with a PLC-based control system, or alternatively, by manual monitoring. In this manner, if necessary, the injection pressure of the air in the channel system 10 may be adjusted and maintained at optimum levels through control of the blower and/or dampers. The channel system 10 may also be placed under vacuum to pull off the excess water associated with any injection pressure rise or which may otherwise accumulate in the system due to external influences, such as rain.

Humidity Control

Similarly, the humidity or moisture content of the air in the channel system may also be controlled to promote healthy sod. Measuring the moisture content within the channel system 10 is accomplished by various known means. For example, moisture meters may be operated in conjunction with a PLC-based control system, or alternatively, by manual monitoring. In this manner, if necessary, the moisture content of the air in the channel system 10 may be adjusted and maintained at optimum levels. Specifically, a further embodiment of the present invention allows moisture to be added to the rootzone and turfgrass.

Through the use of atomizing nozzles installed in the air channel system, it is possible to increase the relative moisture content of the air stream and reduce or eliminate the need for surface water irrigation. The moisture content of the air in the channel system is variably controllable to at least about 50%, more preferably about 90%, and most preferably about 100%.

As discussed above, the system can be operated so as to place the channel system 10 under vacuum, thereby removing excess water from the soil in the turf units. 5 This vacuum helps to accelerate the natural gravity drainage of the water through the soil in the turf units. In addition, when operated under vacuum, the air is drawn down through the soil in the turf units and through the channel system is brought through a separator 46. The separator, in a known fashion, removes water from the moist air stream, providing another mechanism through which moisture is removed from the rootzone layer.

10

Nutrients and Soil Gases

In addition to using direct-fired heated air to warm the system, and thereby take advantage of combustion by-products as a source of nutrients for the system, it should be understood that soluble nutrients, fungicides, and such can also be injected

15 through the atomizing nozzles, maximizing the contact with the plant system while minimizing exposure to personnel and the environment. One of ordinary skill in the art would be readily aware of types and nature of the numerous solubles to inject.

The forced air has a further advantage of providing much needed oxygen to the root system. It is the object of the present invention to allow monitoring of the

20 oxygen levels of the grass and rootzone layer 6 in the turf units 4 so that optimal levels may be maintained. One such system is manufactured by Soil Air Technology, LLC, of Middlefield, CT. Preferably, the oxygen level of the rootzone is between about 10 and 30%) and more preferably between about 15 and 25%. Most preferably, the oxygen level of the rootzone is between about 18 and 23%. Gases other than or in addition to oxygen

25 may be added with the forced air - these rootzone gas concentrations may be monitored as well by any means known to one skilled in the art.

Irrigation System

The turf system of the present invention also includes an irrigation system

30 20 comprising an interconnected network of multiple sizes of tubing and piping. This tubing system allows water to be passed through the system beneath the rootzone and turfgrass. The tubing can be of any material but is preferably polyvinyl chloride ("PNC") tubing. The tubing system comprises mainline tubes, both large and small, as well as lateral tubes. The tubing system is connected together by a plurality of sleeves, fittings,

35 swing joints, and heads. The irrigation tubing should be free of defects or imperfections, such as blisters, internal striations, and cracks. The large mainline pipes should have a diameter of at least about 3 in and preferably about 4 in. Large piping that is sufficient for the present invention is at least Class 200 (SDR 21), Type 1, Grade 1 PNC, and should contain integrally molded bell joint connections. Prefeπed PNC piping conforms to ASTM D1784 and D2241 standards. The small mainline pipes have a diameter of less than about 2.5 in and preferably less than about 2 in. Small piping that is sufficient for the present invention is at least Schedule 21, Class 200, Type 1120-1220 PNC. Preferably, the small piping conforms to ASTM D1784 and D2241 standards. The irrigation system 20 of the present invention further contains rubber gasket rings which preferably conform to the ASTM 1869 standard. The lateral pipes can have any diameter but are preferably less than about 2 in. Most preferably, the lateral piping has a diameter of less than about 1.5 in. Prefeπed lateral piping, sufficient for the present invention, is at least Schedule 21, Class 200, Type 1120-1220 PVC, and conforms to ASTM D1784 and D2241 standards.

The fittings for the large piping are preferably of the gasket type and can be of any material, such as PNC or ductile iron. Ductile iron fittings, such as HARCO Deep Bell manufactured by Harrington Corp. of Lynchburg, NA, are prefeπed and are preferably grade 70-55-05 in accordance with the ASTM A-536 standard. The fittings for the small and lateral piping should be in accordance with the ASTM D 2467 standard, and be at least Schedule 40, socket type, Type 1, Grade 1 PNC with solvent weld or threaded connections in conformance with the ASTM D1784 and D2466 standards. If swing joints are used, many types are sufficient. However, it is prefeπed that the swing joints be similar to Lasco triple swing joints. The irrigation system 20 further contains heads which may be arranged with a variety of nozzle patterns, as is known in the art. The heads are preferably at least one of rotary gear driven, have rubber caps, and have a stainless steel riser. The heads are preferably mounted at least 0.5 in below grade installation.

Warning Track Units

In some instances, it is desirable to provide non-turf surfaces contiguous with the turf surface. For example, in the context of a football field, there is often heavy traffic, even including motorized vehicles which operate at playing field level, outside the actual boundaries of the playing field. Because such traffic is extremely damaging to natural turf, the system may include warning track units, which are units which are structurally compatible with the turf units, but which do not contain soil and turf, but rather are provided with manufactured inserts. For example, as shown in FIG. 5, a lightweight warning track unit consists of a growing tray 5, just as used in the turf units 4, together with a plurality of support members 51, a horizontal support layer 53, and a surface layer 55. In a preferred embodiment, the support members are large-diameter PNC pipe, cut to be securely seated within the growing pan and to present flat horizontal upper ends. The horizontal support layer is constructed from a strong, light material, such as a light wood, such as balsa wood. The surface layer 55 is a suitable traffic surface, such as rubber. Because the warning track units are based on the same growing pans as the turf units, they are fully structurally compatible with the turf units. Accordingly, these warning track units may advantageously be used in any region, of a field provided with the turf units of the present invention, in which a natural grass surface is not required.

The invention described and claimed herein is not to be limited in scope by the specific embodiments herein disclosed, since these embodiments are intended solely as illustrations of several aspects of the invention. Any equivalent embodiments are intended to be within the scope of this invention. Indeed, various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the appended claims.

Claims

THE CLAIMSWhat is claimed is:

1. A turf system comprising: a plurality of turf units disposed on an underlying surface in proximity to each other to form a turf unit array having a turf surface, the turf units containing a plant growing medium in which a plurality of turf plants is growing, the growing medium comprising a rootzone layer, the turf unit array having an outer surface facing the underlying surface; the outer surface of the turf unit array and the underlying surface forming a channel system through which an airstream can flow; and a pump for forcing the airstream through the channel system and into the rootzone layer of at least one of the turf units.

2. The turf system of claim 1 , further comprising a plurality of locator pads interacting with the turf units, the locator pads providing repeatable alignment of the turf units with substantially no gaps in the turf surface.

3. The turf system of claim 1 , wherein the turf units have a rectangular shape as viewed from above.

4. The turf system of claim 1 , further comprising a heating system.

. The turf system of claim 4, wherein the heating system comprises a direct-fired furnace which directly heats the airstream which is forced through the channel system.

6. The turf system of claim 4, wherein the heating system comprises a direct-fired furnace and a heat exchanger, the furnace heating a first body of air and the heat exchanger transferring some of the heat energy from the first body of air to a second body of air without mixing of the first and second bodies of air, the second body of air being forced through the channel system.

7. The turf system of claim 1 , wherein the turf plants comprise turfgrass.

8. The turf system of claim 1, wherein the rootzone layer comprises a mixture of processed sand and peat.

9. The turf system of claim 8, wherein the rootzone layer has a depth of about 5 to 7 in.

10. The turf system of claim 1 , wherein the growing medium further comprises a drainage layer.

11. The turf system of claim 10, wherein the drainage layer comprises gravel.

12. The turf system of claim 11 , wherein the drainage layer has a depth of between about 3 to 5 in.

13. The turf system of claim 1 , wherein the growing medium has a first temperature and the air has a second temperature.

14. The turf system of claim 13, wherein the second temperature is less than about 70% greater than the first temperature.

15. The turf system of claim 14, wherein the second temperature is less than about 50% greater than the first temperature.

16. The turf system of claim 13, wherein the first and second temperatures have a difference of less than about 40 °F.

17. The turf system of claim 16, wherein the difference is less than about 10°F.

18. The turf system of claim 13, wherein the second temperature is between about 70°F and about 120°F.

19. The turf system of claim 18, wherein the second temperature is between about 70 °F and about 80 °F.

20. The turf system of claim 4, further comprising a system for introducing a liquid into the airstream.

21. The turf system of claim 20, further comprising atomizing nozzles disposed in the channel system, the atomizing nozzles for injection of atomized fluid into the airstream in the channel system.

22. The turf system of claim 20, wherein the fluid injected by the atomizing nozzles comprises water, and injection of the water effects cooling of the turfgrass rootzone layer relative to the temperature of the rootzone layer prior to injection of the water.

23. The turf system of claim 20, further comprising: a sensor sensing the rootzone moisture content and generating a signal based thereon; a closed-loop control system, responsive to the signal, provided with a predetermined setpoint value for the rootzone moisture content, the closed loop control system controlling one or more of the heating system, pump, and atomizing nozzles, so as to bring the sensed rootzone moisture content closer to the setpoint value.

24. The turf system of claim 4, further comprising: a sensor sensing the rootzone temperature and generating a signal based thereon; a closed-loop control system, responsive to the signal, provided with a predetermined setpoint value for the rootzone temperature, the closed loop control system controlling one or both of the heating system and the pump so as to bring the sensed rootzone temperature closer to the setpoint value.

25. The turf system of claim 1 , further comprising one or more sensors sensing the value of one or more system physical parameters, the parameters being selected from the group of rootzone temperature, channel system airstream temperature, rootzone moisture content, channel system airstream humidity, and channel system airstream pressure.

26. The turf system of claim 25, further comprising a closed-loop control system for control of the one or more system physical parameters whose values are being sensed.

27. The turf system of claim 1 , further comprising one or more warning track units.

28. The turf system of claim 1 , further comprising a system for introducing particulate matter into the airstream.

29. A turf system comprising: a plurality of turf units disposed on an underlying surface in proximity to each other to form a turf unit array, each turf unit having a lower surface and containing a plant growing medium in which a plurality of turf plants is growing, the turf plants forming a grass surface, the growing medium comprising at least a rootzone layer; the lower surface of the turf unit aπay and the underlying surface forming a channel system through which air can flow; a pump for forcing the air through the channel system and into the rootzone layer of at least one of the turf units; one or more sensors for sensing a system temperature and generating a signal indicative thereof, the system temperature being selected from the group of: (i) temperature of the air in the channel system or (ii) temperature of the rootzone layer; a closed-loop control system, responsive to the signal from the sensor(s) and a predetermined system temperature setpoint value, controlling at least one of the pump and the heating system, such that heated air is supplied to the rootzone layer of at least one of the turf units when the signal from the sensors indicates a system temperature below the setpoint value.

30. The turf system of claim 29, further comprising a plurality of locator pads interacting with the turf units, the locator pads providing repeatable alignment of the turf units with substantially no gaps in the turf surface.

31. The turf system of claim 29, wherein the turf units have a rectangular shape as viewed from above.

32. The turf system of claim 29, further comprising a heating system for optionally heating the air.

33. The turf system of claim 32, wherein the heating system comprises a direct-fired furnace which directly heats the air which is forced through the channel system.

34. The turf system of claim 32, wherein the heating system comprises a direct-fired furnace and a heat exchanger, the furnace heating a first body of air and the heat exchanger transferring some of the heat energy from the first body of air to a second body of air without mixing of the first and second bodies of air, the second body of air being forced through the channel system.

35. The turf system of claim 29, wherein the growing medium has a first temperature, the air has a second temperature, the second temperature being less than about 70% greater than the first temperature.

36. The turf system of claim 29, wherein the growing medium has a first temperature, the air has a second temperature, the second temperature being less than about 50%) greater than the first temperature.

37. The turf system of claim 29, wherein the growing medium has a first temperature, the air has a second temperature, the first and second temperatures having a difference of less than about 40 °F.

38. The turf system of claim 29, wherein the growing medium has a first temperature, the air has a second temperature, the first and second temperatures having a difference of less than about 10°F.

39. The turf system of claim 29, wherein the air has a temperature between about 70°F and about 120°F.

40. The turf system of claim 29, wherein the air has a temperature between about 70 °F and about 80 °F.

41. The turf system of claim 29, further comprising a system for introducing a liquid into the airstream.

42. The turf system of claim 41 , further comprising atomizing nozzles disposed in the channel system, the atomizing nozzles for injection of atomized fluid into the air in the channel system.

43. The turf system of claim 41 , wherein the fluid inj ected by the atomizing nozzles comprises water, and injection of the water effects cooling of the turfgrass rootzone layer relative to the temperature of the rootzone layer prior to injection of the water.

44. The turf system of claim 41 , further comprising: a sensor sensing the rootzone moisture content and generating a signal based thereon; a closed-loop control system, responsive to the signal, provided with a predetermined setpoint value for the rootzone moisture content, the closed loop control system controlling one or more of the heating system, pump, and atomizing nozzles, so as to bring the sensed rootzone moisture content closer to the setpoint value.

45. The turf system of claim 32, further comprising: a sensor sensing the rootzone temperature and generating a signal based thereon; a closed-loop control system, responsive to the signal, provided with a predetermined setpoint value for the rootzone temperature, the closed loop control system controlling one or both of the heating system and the pump so as to bring the sensed rootzone temperature closer to the setpoint value.

46. The turf system of claim 29, further comprising one or more sensors sensing the value of one or more system physical parameters, the parameters being selected from the group of rootzone temperature, channel system airstream temperature, rootzone moisture content, channel system airstream humidity, and channel system airstream pressure.

47. The turf system of claim 46, further comprising a closed-loop control system for control of the one or more system physical parameters whose values are being sensed.

48. The turf system of claim 29, further comprising one or more warning track units.